The present invention relates to methods and systems for controlling a steering system, and more particularly to methods and system for controlling the on-center feel of an electric power steering system.
Vehicle steering systems are typically constructed such that when a driver does not apply steering torque to the steering wheel, and the vehicle is moving, the vehicle steering tends to return to the center, or straight line of travel, position. This return-to-center function is in response to road forces acting on the turned front tires of the moving vehicle that tend to force the turned tires to the neutral (center) position.
In electric power steering systems, a command may be generated that controls an electric power steering motor to provide a return-to-center position force. The force commanded to the motor overcomes the steering friction and allows the return-to-center function. Upon reaching an on-center position, electric power steering systems typically receive a near-zero torque assist command (similar to conventional manual steering systems), but inertia of the electric power steering motor and back electromotive force (EMF) must be overcome. This combination can result in a notable difference in driving feel between electric power steering systems and conventional manual steering systems.
Accordingly, it is desirable to provide control systems and methods that generate improved command signals for electric power steering motors to be like the manual steering system for near center steering position.